Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $102.94   11.635%   $114.9171   $114.92   $114.90   $114.90  
  Purchase #2 $210.88   11.354%   $234.8233   $234.82   $234.80   $234.80  
  Purchase #3 $114.85   5.252%   $120.8819   $120.88   $120.90   $120.90  
  Purchase #4 $218.53   3.686%   $226.585   $226.59   $226.60   $226.60  
  Purchase #5 $77.83   8.512%   $84.4549   $84.45   $84.45   $84.50  
  Purchase #6 $153.56   12.535%   $172.8087   $172.81   $172.80   $172.80  
  Purchase #7 $169.54   5.269%   $178.4731   $178.47   $178.45   $178.50  
  7 purchase totals = $1,048.13       $1,132.9440   $1,132.94   $1,132.90   $1,133.00